1. Field of the Invention
This invention relates to chemical compounds which are used as stabilizers for protecting polymers against degradation that is induced by exposure to ultraviolet light. Specifically, the invention concerns such a UV-stabilizer, which is a bisurea compound that includes two 2-(2'-hydroxyphenyl)benzotriazole groups.
2. Description of the Prior Art
Many compounds are known in the art for use as UV-stabilizers for organic polymers. Among the known UV-stabilizers are 2-(2'-hydroxyphenyl)benzotriazoles of the type disclosed by Canadian Patent 1,197,246 to Ciba-Geigy AG. Ciba-Geigy sells such UV-stabilizers under the "Tinuvin" trade names. These include, for example, "Tinuvin" 213, also referred to as "Tinuvin" 1130, which is mainly the 2-[2-(2-hydroxy-ethoxy)ethoxy]ethylester of 3-(2H-benzotriazol-2-yl)-4-hydroxy-5-(1,1-dimethylethyl)-benzene propanoic acid).
Although the 2-(2'-hydroxyphenyl)benzotriazoles have been useful in many organic polymers, when used as UV-stabilizing additives in spandex fibers certain shortcomings are evident. For example, spandex fibers often are converted into fabrics or garments that are subjected to solvent scouring and various dry-cleaning solvents. Solvents, such as perchloroethylene and other non-polar solvents, are used extensively. However, such solvents extract the hydroxy-benzotriazole additives from the polymeric fibers, thereby reducing the UV-protection for the fibers. Also, some of the known hydroxyphenyl-benzotriazole UV-light stabilizers have caused accelerated degradation of spandex in the presence of aqueous hypochlorite solutions. Such solutions are commonly used as laundry bleaches. Furthermore, some known hydroxyphenyl-benzotriazole stabilizers have a tendency to form colored complexes when exposed to copper ions. In spandex, these stabilizers can cause yellow discoloration during textile finishing or in laundering, if the water used contains copper ions (e.g., as might be present in water supplied through copper pipes).
It is a purpose of this invention to overcome, or at least significantly reduce, the above-recited shortcomings of the known hydroxyphenyl-benzotriazole UV-stabilizers and to provide a UV-stabilizer that is not readily extracted from polymer by scouring and dry-cleaning solvents, is relatively unaffected by common laundry bleaches and is not detrimentally affected by the presence of copper ions.
Although not related to 2-(2'-hydroxyphenyl)benzotriazole UV-light stabilizers, bisurea compounds per se, as well as for other types of stabilizers, are known in the art, as for example from Japanese Patent 46/13143 to Teijin Ltd.